In traditional cellular communication, voice, data and other traffic between two UEs should be exchanged through evolved NodeBs (eNBs) where they reside, and a core network. The Device to Device (D2D) technology refers to that data can be transmitted directly between adjacent UEs in a short-distance range over a direct link without being forwarded through a central node (i.e., an eNB).
Due to its short-distance communication characteristic and direct communication mode, the D2D technology has the following advantages: (1) a higher data rate, a lower delay, and a lower power consumption can be achieved by virtue of direct communication conducted between the UEs over a short distance; (2) a more efficient spectrum resources utilization can be achieved by virtue of UEs distributed widely in the network, and the short-distance link of the D2D communication; (3) a demand for sharing local data in services, e.g., wireless P2P, etc., can be satisfied, and a more flexible and more adaptive data service can be supplied by virtue of direct communication mode of D2D (4) a coverage area of network can be extended by virtue of D2D direct communication adopted by a large number of widely distributed UEs.
In Long Term Evolution (LTE) system, D2D communication refers to such a D2D communication process, controlled by the LTE system, operating in a LTE authorized frequency band. The D2D communication in LTE system can make full use of the advantages of the traditional D2D technology, and some problems in the traditional D2D technology, e.g., uncontrollable interference, etc., can be addressed by the control under LTE system.
If D2D communication is applied to the authorized frequency band of LTE system, then radio resources will be shared between the D2D communication and cellular communication, where the radio resources can be shared in an orthogonal mode or reusing mode. Here, the radio resources sharing in the orthogonal mode refers to that the radio resources are orthogonally divided in a static or dynamic manner to be accessed by cellular communication and D2D communication; and the radio resources sharing in the reusing mode refers to that the cellular resources being accessed are reused reasonably by D2D communication, while interference is limited to some level range.
If the same radio resources are accessed in the reusing mode by D2D communication and cellular communication, then interference between them may occur. Taking cellular uplink radio resources reused as an example, a first type of interference refers to interference caused by a D2D signal to a cellular signal, which may degrade the quality of cellular communication, and the strength of the first type interference is determined by power in D2D transmission, and the distance between a D2D transmitter and an eNB; and a second type of interference refers to interference caused by a cellular signal to a D2D signal, and the strength thereof is determined by the distance between a cellular transmitter and a D2D receiver, where cellular transmission at a short distance from the D2D receiver may impose strong interference to D2D communication.